1. Technical Field
The present invention relates to a three-dimensional image measuring apparatus and method for acquiring three-dimensional shape data on a measuring object using photographed image data. The present invention is directed to image measurement of measuring objects at short to middle distances, where significant projection distortion occurs in images photographed in stereo, rather than long-distance objects such as in aerial photography.
2. Related Art
Methods for obtaining 3D data on a working object, a manufacturing object or geographic features include an approach using a measuring instrument (total station) that obtains 3D data at points based on the distance and angle to an object, a motor-driven measuring instrument that acquires data in a surface manner by scanning with a beam, or a laser scanner that acquires data by rapidly oscillating a laser beam.
Meanwhile, other methods include a stereo image measurement approach, in which 3D data is obtained at points or in a surface manner by stereo measurement of stereo images photographed using an object and a comparative calibration body.
Both approaches have an advantage of being able to obtain 3D data in a non-contact manner.
In the former approach, 3D data can be automatically acquired simply when the installation is complete. However, since the bare information which can be acquired includes no image but only distance data and angle data, the details of the measuring object and its surroundings cannot be known. Thus, another instrument needs to be used to photograph an image and affix the image to the distance data. The former approach also involves a serious problem of disturbance noise due to long hours of installation for measurement.
In the latter approach, cameras perform the photographing only momentarily, which causes no problem of disturbance noise. In addition, since images are used in the measurement, there is no need to affix images afterward.
However, measuring objects with significant projections and depressions are difficult to measure in both approaches.
It has become apparent with the latter approach, that photographed images of some measuring objects, in particular at short to middle distances, are not a little affected by projection distortion due to their projections and depressions, and that it is therefore difficult to perform precise three-dimensional position measurement using such images.
The present invention has been made to solve the above-mentioned problem, and therefore has an object to provide a three-dimensional image measuring apparatus and method capable of measuring projections and depressions on a surface of an object with fine precision, as well as ensuring stable convergence, even for stereo images with significant project distortion.